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btrfs-progs: fix unaligned accesses v2 

gcc optimizes out the memcpy calls at -O2 and -Os.

Replacing memcpy with memmove does't work - gcc treats memmove
the same way it treats memcpy.

This patch brings in {get|put}_unaligned_le{16|32|64} (using the
packed struct method), and uses them in the failing get/set calls.

On architectures where unaligned accesses are cheap, these unaligned
macros should be optimized out by the compiler.

Signed-off-by: Ben Peddell <klightspeed@killerwolves.net>
master
Ben Peddell 2013-01-27 15:45:43 +10:00 committed by David Sterba
parent 272c049152
commit 7b668965f0
2 changed files with 15 additions and 6 deletions
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8
ctree.h
View File

@ -1086,19 +1086,15 @@ static inline u##bits btrfs_##name(struct extent_buffer *eb, \
type *s) \
{ \
unsigned long offset = (unsigned long)s; \
u##bits m; \
type *p = (type *) (eb->data + offset); \
memcpy(&m, &p->member, sizeof(m)); \
return le##bits##_to_cpu(m); \
return get_unaligned_le##bits(&p->member); \
} \
static inline void btrfs_set_##name(struct extent_buffer *eb, \
type *s, u##bits val) \
{ \
unsigned long offset = (unsigned long)s; \
u##bits m; \
type *p = (type *) (eb->data + offset); \
m = cpu_to_le##bits(val); \
memcpy(&p->member, &m, sizeof(m)); \
put_unaligned_le##bits(val, &p->member); \
}
#define BTRFS_SETGET_STACK_FUNCS(name, type, member, bits) \

13
kerncompat.h
View File

@ -267,6 +267,19 @@ typedef u64 __bitwise __be64;
#define cpu_to_le16(x) ((__force __le16)(u16)(x))
#define le16_to_cpu(x) ((__force u16)(__le16)(x))
#endif
struct __una_u16 { u16 x; } __attribute__((__packed__));
struct __una_u32 { u32 x; } __attribute__((__packed__));
struct __una_u64 { u64 x; } __attribute__((__packed__));
#define get_unaligned_le8(p) (*((u8 *)(p)))
#define put_unaligned_le8(val,p) ((*((u8 *)(p))) = (val))
#define get_unaligned_le16(p) le16_to_cpu(((const struct __una_u16 *)(p))->x)
#define put_unaligned_le16(val,p) (((struct __una_u16 *)(p))->x = cpu_to_le16(val))
#define get_unaligned_le32(p) le32_to_cpu(((const struct __una_u32 *)(p))->x)
#define put_unaligned_le32(val,p) (((struct __una_u32 *)(p))->x = cpu_to_le32(val))
#define get_unaligned_le64(p) le64_to_cpu(((const struct __una_u64 *)(p))->x)
#define put_unaligned_le64(val,p) (((struct __una_u64 *)(p))->x = cpu_to_le64(val))
#endif
#ifndef noinline